Prevalence and risk factors for HIV, hepatitis B, and hepatitis C in people with severe mental illness: a total population study of Sweden

BACKGROUND Severe mental illness is associated with increased morbidity and mortality. The elevated risk of blood-borne viruses (BBVs) in people with severe mental illness is of concern, but the full extent of this problem is unclear. We aimed to determine the prevalence of and risk factors for BBVs in people with severe mental illness. METHODS In this nationwide, population-based, cross-sectional study, we estimated the point prevalence of HIV, hepatitis B (HBV), and hepatitis C (HCV) in people with severe mental illness, including the total adult (≥18 years) Swedish population. We defined severe mental illness as a clinical diagnosis of schizophrenia, schizoaffective disorder, bipolar disorder, or other psychotic illness according to the Swedish version of the International Statistical Classification of Diseases version 8, 9, or 10. We used multivariable logistic regression to determine the odds of BBVs in individuals with severe mental illness, relative to the general population, and to identify independent risk factors (age, sex, immigration status, socioeconomic status, education, and substance misuse) for BBV infection. We also did a sensitivity analysis excluding BBV diagnoses made before the introduction of the Register for Infection Disease Control (1997). FINDINGS Of 6 815 931 adults in Sweden, 97 797 (1·43%) individuals had a diagnosis of severe mental illness. Prevalence of BBVs was elevated in people with severe mental illness, of which 230 (0·24%) had HIV, 518 (0·53%) had HBV, and 4476 (4·58%) had HCV. After accounting for sociodemographic characteristics, the odds of HIV were 2·57 (95% CI 2·25-2·94, p<0·0001) times higher in people with severe mental illness than in the general population, whereas the odds of HBV were 2·29 (2·09-2·51, p<0·0001) times higher and the odds of HCV were 6·18 (5·98-6·39, p<0·0001) times higher. Substance misuse contributed most to the increased risk of BBV: after adjustment, odds ratios were 1·61 (1·40-1·85, p<0·0001) for HIV, 1·28 (1·16-1·41, p<0·0001) for HBV, and 1·72 (1·67-1·78, p<0·0001) for HCV. INTERPRETATION Our results highlight the need to address the issue of higher prevalence of BBVs in people with severe mental illness and identify interventions preventing infection. Targeting of comorbid substance misuse would have particular effect on reduction of BBV prevalence in this population. FUNDING Medical Research Council and Swedish Research Council.